Specular luminance is defined as the relative light reflectance factor of a sample in the specular direction. The D25 1413 standard, developed by the PSA Peugeot Citroen group, Europe's second largest automobile manufacturer, defines a measurement method for the gloss measurement of paint coatings in rubber and plastics. This measurement method was developed to correlate visual observations of surface brightness made at corresponding angles. The light beam is directed to the sample at a certain angle and the light reflected from the sample is collected and measured. All specular gloss values are based on a primary reference standard, which is a high gloss black glass with a designated specular gloss value of 100. Three basic angles of incidence of 20, 60 and 85 degrees are used for specular gloss measurement of optical plastic samples. As the angle of incidence increases, the brightness value of any surface also increases.
Gloss meters basically consist of an optical assembly on which an incandescent light source, a concentrator lens, and a projection or source lens are located. The incident beam generated by this assembly is directed towards the test specimen. A sensitive photo detector collects the reflected light and generates an electrical signal that is amplified to energize the analog or digital panel meter to display the value in luminance units.
The operation of brightness meters is quite simple. The device is switched on and placed behind the black glass primary standard. The control knob is set so that the counter displays the value assigned to the primary standard. Then the sensor is placed on the sample surface and the brightness value is read directly from the analog or digital display. The linearity of the device is routinely checked by placing the sensor on a white secondary standard, where it should read within 1.0 brightness unit of the assigned value of that standard.
The choice of illumination angle (20, 60 and 85 degrees) depends on the brightness value. Gloss measurement in paints is generally done for the following purposes:
Among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides test services for the gloss measurement of paint coatings in rubber and plastics within the scope of D25 1413 standard, with its trained and expert staff and advanced technological equipment.
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